Materials

Purpose

To help students understand the scientific process by exploring how a bird can sit on his/her eggs without breaking them.

Context

Students at this grade level are still fascinated by animals and the ways in which they behave. This grade level is also the period in which many students do activities in school involving eggs, including chicken eggs and turtle eggs. This lesson is meant to take advantage of students' natural curiosity about this subject by challenging them to do an activity involving eggs to test a hypothesis. In particular, students will conduct an experiment where they will use eggs to support some heavy books.

When doing this lesson with your class, it is important to remember that from the earliest grades, students should experience science in a form that engages them in the active construction of ideas and explanations and enhances their opportunities to develop the abilities of doing science. Teaching science as inquiry provides you with the opportunity to develop student abilities and to enrich student understanding of science. Students should do science in ways that are within their developmental capabilities.

Upper elementary school students may not understand experimentation as a method of testing ideas, but rather as a method of trying things out or producing a desired outcome. In addition, students of all ages may overlook the need to hold all but one variable constant, although elementary students already understand the notion of fair comparisons, a precursor to the idea of "controlled experiments." Finally, students of all ages find it difficult to distinguish between a theory and the evidence for it, or between description of evidence and interpretation of evidence. (Benchmarks for Science Literacy, p. 332.)

Motivation

To begin this lesson, students should use their Big Egg Mystery student esheet to go to An Egg Is Quiet on PBS Kids. This video features a reading of the book, An Egg Is Quiet by Dianna Aston. As an alternative, you could choose to obtain a hard copy and read this book aloud with your class. An Egg Is Quiet explores eggs in their many forms, from the delicate pale green ova of the green lacewing to the mammoth bulk of an ostrich egg. Aston's text celebrates eggs' diversity, commenting on size, shape, coloration, and where they might be found.

Once students have followed along with this reading, ask them questions like these (students can write their answers to these questions on the Big Egg Mystery student sheet):

As you read along with this book, what do you notice about the eggs? Are they all the same? What are some of the eggs' colors, shapes, sizes, and textures?

(The eggs are not all the same. The eggs' colors include blue, white, brown, etc. The eggs' shapes include round, oval, tubular, etc. The eggs' sizes include as small as a grain of rice or as big as a basketball. The eggs' textures can be rough or smooth.)

When it comes to the color of an egg, what is important about the color?

(The markings on some eggs help them blend in with their surroundings. This is called camouflage.)

When it comes to the shape of an egg, what is important about the shape?

(The shape of eggs can help them fit in certain spots, or, like the pointy end of seabird eggs, help them roll around in safe little circles and not off the cliff.)

When it comes to the size of an egg, what is important about the size?

(The size of the egg often depends on the size of the animal who laid it.)

What you are looking for with all of these questions is that students understand that these features of eggs help the animal growing inside the egg survive in a particular environment.

Even though this was not discussed in the book, why do you think that when a bird sits on his/her eggs, the bird does not break the eggs?

(Answers will vary. Encourage students to provide explanations for their answers.)

Do you think there is a way to find out why a bird does not break his/her eggs by doing an experiment in the classroom?

(Answers will vary. Encourage students to provide explanations for their answers.)

Let students know that in the next part of the lesson, they will have a chance to do an experiment to test their ideas.

Development

In this part of the lesson, you will ask students to form a hypothesis about whether or not egg shells can hold heavy books. This will serve as a model of a bird sitting on eggs. Students will then get to test their hypothesis by performing the Egg Experiment activity.

Before students move on to the egg experiment, provide them with a variety of other eggs that you have brought in. Ask students to observe the eggs. Allow them to hold them, measure them, weigh them (if you have a scale), and gently squeeze them from both the end and middle. They can record their observations on the Egg Observations student sheet. (You may need to be prepared for messes if the eggs break!)

Once students have had a chance to observe the eggs, ask them to share their observations with the class.

You can use the Egg Experiment teacher sheet to help with this part of the lesson. Show students the six eggs that you've arranged in a square. Ask them this question: "Can six egg shells hold 3-4 heavy books such as encyclopedias or dictionaries?" Students will guess "yes" or "no." Record their answers on the blackboard or on some newsprint. Then ask, "Why do you think this is or is not possible?" Again, record their answers on the blackboard or newsprint.

Now have students form a hypothesis about whether or not the eggs will break based on their previous responses. Explain to your students that a hypothesis is an educated guess or prediction of what they think will happen. A good hypothesis could take the form of, "If I do this, then that will happen." So, for the purpose of this activity, students will form a hypothesis about the egg shells and the books. Students can write their hypotheses on the Egg Experiment student sheet.

Now, finish conducting this activity as a class by following the steps outlined on the Egg Experiment teacher sheet.

Once the class has completed this activity, hold a class discussion about what students learned from it. You could ask questions like these:

What did you observe when one of the books was placed on the eggs?

(The eggs did not break.)

Why do you think the eggs did not break?

(Listen to students' explanations, but you may have to explain that the shape of the eggs is the reason they did not break when the book was placed on them—or the bird sits on them. The oval shape applies the same rules of engineering as an arched bridge; the dome-shaped surface can withstand considerable pressure without breaking. This is essential if the eggs are not to crack under the weight of the sitting bird.)

Did this match what you predicted in your hypothesis? Why or why not?

(Answers will vary. Encourage students to explain their answers.)

Do you need to make any changes to your hypothesis now that you've done this activity?

(Answers will vary.)

Are there any other ways in which you could test your hypothesis?

(Encourage students to come up with other ways to do this experiment.)

How is placing books on the eggs like a bird sitting on eggs? How is it different? Is there anything you would change to improve this experiment?

(Answers will vary.)

Assessment

An appropriate assessment for this lesson would be to have students develop their own experiments for testing their hypotheses. For example, what is it about the shape of the eggs that keeps them from breaking when heavy books are placed on them? Students can use the Egg Experiment student sheet to help them develop hypotheses and ideas for their experiments. Be sure to provide students with the materials they need to perform their experiments. Their hypotheses and experiments should demonstrate that students understand that scientific investigations can take different forms and that models are similar to, but not exactly like, the thing being modeled.

Extensions

The Science NetLinks lesson, Color Burst helps students gain experience in conducting simple investigations of their own while working in small groups.

Sink It, another Science NetLinks lesson, provides even more practice with developing a procedure for an experiment.